Loan Stone Estimator
Decorative stone is where bag math goes to die: the difference between 2 tons delivered and 100 bags in the trunk. Enter the bed, pick the depth — get tons, yards and the bag count, all three, before you choose.
Depth rule: at least twice the rock's diameter, or the fabric shows through between stones. One inch of rock in a 3-in bed is decoration; three inches is cover.
How it works
Volume is area × depth, converted to cubic yards. Bulk decorative stone runs about 1.35 tons per cubic yard (1,350–1,400 lb per loose yard is the yard-standard band). Bags assume the common 50-lb (0.5 cu ft class) bag — which is why the bag count explodes: a single ton is 40 bags. The coverage line inverts it: at 3 in deep, one ton covers about 80 sq ft; at 2 in, about 120. Compare that against the per-bag claim on the pallet before believing either.
Formula & worked example
Formula: Cubic yards = area × depth in inches ÷ 12 ÷ 27. Tons = yards × 1.35 (bulk decorative stone). Bags = tons × 2,000 ÷ 50 lb. Coverage per ton = 27 × 12 ÷ depth ÷ 1.35 sq ft.
Worked example: A 200 sq ft bed at 3 in deep: 1.85 cu yd — 2.50 tons bulk, or 100 fifty-pound bags. One ton covers about 80 sq ft at that depth.
When to use this
- You are covering beds or a dry creek with river rock or decorative stone.
- You are deciding between bulk delivery and bagged stone.
- A landscape quote lists tonnage you want to verify.
How to use it, step by step
- Measure the area to cover in square feet.
- Pick depth — at least twice the rock diameter.
- Compare tons (bulk) against the bag count honestly.
- Order bulk past about half a ton.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Area | Bed or feature area in square feet | 50–400 sq ft typical beds |
| Depth | Stone depth in inches | 2 in light cover; 3 in standard; 4–6 in drainage |
| Rock size | Nominal stone diameter | 1 in pea size; 1–2 in standard; 2–4 in cobble |
Another worked example
A smaller bed: 100 sq ft at 2 in deep takes 0.62 cu yd — 0.83 tons bulk, or 34 fifty-pound bags. Under a ton, bags and a hatchback are a defensible choice; at the main example's 2.5 tons, the delivery truck wins by hundreds of dollars and one spine.
Frequently asked questions
How much river rock do I need for 200 sq ft?
At the standard 3-in depth: 1.85 cu yd, which is 2.50 tons bulk — or 100 fifty-pound bags. That gap is the whole bulk-versus-bags decision in one line: past about half a ton, delivery almost always wins.
How much does a ton of stone cover?
About 120 sq ft at 2 in deep, 80 at 3 in, 60 at 4 in. Coverage claims on bag labels usually assume the shallowest depth — check the fine print against your depth, not their best case.
River rock or mulch for beds?
Stone costs more up front, never decomposes, and holds on slopes and in drainage paths; mulch is cheaper, feeds the soil and needs topping up yearly. Many beds end up stone at the drip line and mulch at the plants. The Mulch Calculator sizes the other option.
What size river rock should I buy?
One-to-two inch is the landscape standard — big enough to stay put and look like rock, small enough to shovel and spread. Pea-size (⅜ in) migrates into lawns and paths; 2–4 in cobble is for drainage swales and dry creek beds.
Should I put landscape fabric under stone?
Under stone, yes — it keeps rock from migrating into soil and turns a re-do into a lift-out instead of an excavation. Under mulch, most landscapers skip it: mulch is meant to break down into the bed.
🪨 Crushed stone instead of round rock?
For driveways, bases and drainage in angular crushed stone, the Gravel Calculator works in driveway depths and densities — and compares bulk vs bagged cost.
How do I keep river rock from sinking into the soil?
Landscape fabric under the stone, plus an edge restraint — steel, aluminium or a paver soldier course — so the bed has a boundary the lawn cannot negotiate with.
Does stone get hot enough to hurt plants?
In full-sun hot climates, light-coloured stone reflects heat and dark stone stores it; keep stone a few inches from tender stems and use it under shrubs and in drainage paths rather than against delicate perennials.